Fig. 1. Measurement of the craniocaudal center of mass. The dead animal was placed on its side, with the limbs arranged in a manner that resembled a standing position. The tail was positioned at about a 45° angle in the sagittal plane relative to the long axis of the body; this is approximately the same tail posture that is adopted during normal movement. l, length of platform between knife points; Y_com, distance between knife point and center of mass; W_s, weight of opossum; W_p, weight of knife point platform. See text for formula.